A hand-held device for measuring an analyte concentration has been known from WO 2007/030457 A1 and is used for quantitative analysis of body liquids, for example of urine, blood and interstitial liquid, i.e. for measuring the concentration of medically significant analytes such as lactate, cholesterol and, especially, glucose.
Hand-held devices of that kind can be carried along by the users and are needed, for example, by diabetics who are required to measure their glucose concentration on a sample of blood and/or interstitial liquid several times a day.
The measured values so obtained can be stored in a measured-value storage of the hand-held device for being transferred later to an external evaluation unit, for example a physician's PC. By evaluating the measured values obtained over an extended period of time it is possible to optimize the medical treatment of chronic diseases such as diabetes. Modern hand-held devices therefore comprise a clock so that when the measuring results are evaluated later the development over time of the analyte concentration can be examined in relation to a stored time information.
The time-dependent relation between the different measured values may be distorted when the setting of the clock is altered. This can be avoided when the hand-held device is equipped with an internal clock that cannot be set by the user, a system that has been known from DE 197 33 445 A1. Given the fact that medically relevant analyte concentrations normally are subject to variation according to the rhythm of the day it is, however, desirable to provide the clock of a hand-held device with a setting function so as to allow the time of the day to be adjusted between summer time and winter time or on travels between different time zones. In order to ensure that the evaluation of measured values obtained over an extended period of time will not be distorted, it is necessary that such time adjustments be recorded.
WO 2007/030457 discloses a hand-held device where measured values, as well as the date and hour of the measurement by which the respective value was obtained, are combined to form measured-value datasets which are continuously stored in a measured-value storage. When the clock is set, the amount and direction of the change is stored in a storage (buffer log) provided for that purpose so that the respective information can be taken into account in evaluating the measured values later.